1. Field of the Invention
The present invention relates to a device and method for determining a state of charge (SOC) of a battery. More particularly, the present invention relates to a battery management system for estimating a state such as a SOC using an adaptive filter, and a driving method thereof.
2. Description of the Related Art
A vehicle using an internal combustion engine using gasoline or heavy oil as its principle fuel has serious influence on the generation of environmental pollution such as air pollution. In recent years, much effort is made to develop an electric vehicle or a hybrid vehicle so as to reduce the generation of the environmental pollution.
The electric vehicle refers to a vehicle using a battery engine that operates by an electrical energy outputted from a battery. The electric vehicle uses a battery in which a plurality of rechargeable secondary cells is provided as one pack, as the main power source for the electric vehicle. Thus, the electric vehicle has an advantage in that there is no discharge gas and the noise of the electric vehicle is very small.
The hybrid vehicle refers to an intermediary vehicle between the vehicle using the internal combustion engine and the electric vehicle. The hybrid vehicle uses two or more power sources, for example, the internal combustion engine and the battery engine. At present, the hybrid vehicle using the internal combustion engine and a fuel cell for continuously supplying hydrogen and oxygen while inducing a chemical reaction to directly obtain an electrical energy is being developed.
In the vehicle using electrical energy, a performance of the battery has a direct influence on the performance of the vehicle. Thus, each battery cell should not only have an excellent performance, but also a battery management system (BMS) for measuring the voltage of each battery cell and the voltage and the current of the whole battery. Therefore, effectively managing a charge and discharge of each battery cell is seriously required.
The contemporary battery management system uses a method for estimating the state of charge (SOC) by ampere counting. Also, the contemporary battery management system uses a method for previously recognizing a relationship between the SOC and elements such as an open circuit voltage (OCV), a discharge voltage, an internal resistance, a temperature, or a discharge current, detecting at least two elements, and subsequently detecting the SOC associated with the detected elements based on the recognized relationship between the SOC and the detected elements.
In the contemporary SOC estimation method, an error caused by the ampere counting can occur. Even though the relationship between the OCV and the SOC is recognized, it should be calculated at each battery using a complex experimental method since there is a difference in the characteristic of each battery. Accordingly, the contemporary method causes the error or requires the complex experiment method.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not exist among the prior art that is already known in this country to a person of ordinary skill in the art.